Beacon transmit power schemes

ABSTRACT

In a multi-level power transmission scheme, an access point transmits at one power level, while repeatedly transmitting at a burst power level for short periods of time. For example, a femto cell may transmit a beacon with periodic high power bursts of short duration, while the femto cell transmit power also undergoes high power bursts aligned with the beacon bursts. In a network listen-based power control scheme, an access point listens for one or more parameters sent over-the-air by the network and then defines transmit power based on the received parameter(s). In some aspects, beacon transmit power may be set based on a defined outage radius parameter and the total received signal power on a channel. In some aspects, access point transmit power may be set based on a defined coverage parameter and the received energy associated with signals from access points of a certain type.

CLAIM OF PRIORITY

This application claims the benefit of and priority to commonly ownedU.S. Provisional Patent Application No. 61/228,475, filed Jul. 24, 2009,and assigned Attorney Docket No. 092907P1, the disclosure of which ishereby incorporated by reference herein.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to concurrently filed and commonly ownedU.S. patent application Ser. No. ______, entitled “ACCESS POINT TRANSMITPOWER SCHEMES,” and assigned Attorney Docket No. 092907U2, thedisclosure of which is hereby incorporated by reference herein.

BACKGROUND

1. Field

This application relates generally to wireless communication and morespecifically, but not exclusively, to transmit power control schemes.

2. Introduction

A wireless communication network may be deployed over a definedgeographical area to provide various types of services (e.g., voice,data, multimedia services, etc.) to users within that geographical area.In a typical implementation, access points (e.g., corresponding todifferent macro cells) are distributed throughout a network to providewireless connectivity for access terminals (e.g., cell phones) that areoperating within the geographical area served by the network.

As the demand for high-rate and multimedia data services rapidly grows,there lies a challenge to implement efficient and robust communicationsystems with enhanced performance. To supplement conventional networkaccess points (e.g., macro access points), small-coverage access pointsmay be deployed (e.g., installed in a user's home) to provide morerobust indoor wireless coverage or other coverage to mobile units. Suchsmall-coverage access points may be referred to as, for example, femtocells, femto access points, access point base stations, home NodeBs, orhome eNodeBs. Typically, such small-coverage base stations are connectedto the Internet and the mobile operator's network via a DSL router or acable modem.

In general, at a given point in time, an access terminal will be servedby a given one of the access points in a network. As the access terminalroams throughout the network, the access terminal may move closer toanother access point. Under certain circumstances, the access terminalmay then reselect to the other access point (e.g., be handed-over fromits current serving access point to the other access point). Forexample, to enable an access terminal to access the services provided byan associated femto cell (e.g., a home femto cell), it may be desirableto hand-over the access terminal from a current serving macro cell tothe femto cell as soon as the access terminal enters the coverage areaof the femto cell.

Accordingly, there is a need for techniques to ensure that an accessterminal (e.g., idle user equipment) consistently discovers andreselects to a femto cell when the access terminal arrives at the femtocell. Moreover, it is desirable to achieve this irrespective of thelocation of the femto cell (e.g., the proximity of the femto cell to themacro access point) and without significantly affecting the coverage ofthe macro cell (e.g., without creating outage areas for access terminalscommunicating with the macro cell).

SUMMARY

A summary of sample aspects of the disclosure follows. In the discussionherein, reference to the term aspects may refer to one or more aspectsof the disclosure.

The disclosure relates in some aspects to techniques for determiningtransmit power for an access point. Various techniques are described fordefining transmit power in a manner that facilitates discovery of anaccess point by a nearby access terminal, while mitigating any negativeimpact that transmissions by the access point may have on serviceprovided by a neighboring access point. For example, transmit power maybe defined for a femto cell in a manner that facilitates reselection tothat femto cell by access terminals authorized to access the femto cell,while mitigating outages (e.g., call drops) at access terminalsaccessing a nearby macro cell that may otherwise occur as a result ofthe transmissions by the femto cell.

The disclosure relates in some aspects to a multi-level powertransmission scheme. For example, an access point may usually transmitat a certain power level, but then occasionally (e.g., periodically)transmit at a burst power level (i.e., a higher power level) for shortperiods of time. In some aspects, this multi-level power scheme may beused for normal access point transmissions (e.g., data transmissions)and/or for beacon transmissions. As a specific example, a femto cell maytransmit a jamming beacon on a macro cell frequency with periodic highpower bursts of short duration. In addition, the femto cell transmitpower also may undergo periodic high power bursts.

The disclosure relates in some aspects to transmitting bursts in asynchronized manner. For example, a femto cell may be configured suchthat the femto cell's transmit power bursts are synchronized (e.g.,aligned) with the femto cell's beacon bursts. The use of suchsynchronized bursts may facilitate reselection to the femto cell by anyauthorized access terminals in the vicinity of the femto cell. Forexample, upon detecting a beacon burst from a femto cell, an accessterminal may commence searching for other transmissions (e.g., pilotsignals) from the femto cell. Since these other transmissions will besent at a higher power during the burst period in accordance with theteachings herein, the access terminal will be able to more readilyacquire these signals from the femto cell. Consequently, uponacquisition of these signals (e.g., pilot signals), the access terminalmay initiate reselection to the femto cell.

The disclosure relates in some aspects to network listen-based powercontrol. Here, an access point may listen for one or more parameterssent over-the-air by the network (e.g., by a macro cell) and then defineone or more transmit power values based on the received parameter(s).For example, beacon burst power at a femto cell may be set based on anSintersearch parameter broadcast by a macro cell. Also, femto cell poweror beacon power may be set based on a Qqualmin parameter broadcast by amacro cell.

The disclosure relates in some aspects to determining beacon transmitpower based on total received signal power on a channel and based on adefined outage radius parameter. For example, beacon power at a femtocell may be set based on the total received signal power measured on amacro channel at the femto cell and based on a parameter representingthe path loss from the femto cell at which the femto cell beacon willlikely cause macro cell Ecp/Io at an access terminal to fall below aspecified minimum value (e.g., Qqualmin).

The disclosure relates in some aspects to determining access pointtransmit power based on the received energy associated with signals fromaccess points of a certain type and based on a defined coverageparameter. For example, femto cell power at a femto cell may be setbased on the energy received from all macro cells on a channel and basedon a path loss parameter representative of the boundary of the coverageof the femto cell.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other sample aspects of the disclosure will be described inthe detailed description and the appended claims that follow, and in theaccompanying drawings, wherein:

FIG. 1 is a simplified block diagram of several sample aspects of acommunication system adapted to provide multi-level power control;

FIG. 2 is a flowchart of several sample aspects of operations that maybe performed to provide synchronized burst transmissions;

FIG. 3 is a simplified diagram of sample outage and beacon coverageregions;

FIG. 4 is a flowchart of several sample aspects of operations that maybe performed to determine beacon transmit power based on a receivedparameter;

FIG. 5 is a flowchart of several sample aspects of operations that maybe performed to determine beacon transmit power based on total receivedpower and a defined outage radius parameter;

FIG. 6 is a flowchart of several sample aspects of operations that maybe performed to determine access point transmit power based on areceived parameter;

FIG. 7 is a flowchart of several sample aspects of operations that maybe performed to determine access point transmit power based on receivedenergy and a defined coverage parameter;

FIG. 8 is a simplified block diagram of several sample aspects ofcomponents that may be employed in communication nodes;

FIG. 9 is a simplified diagram of a wireless communication system;

FIG. 10 is a simplified diagram of a wireless communication systemincluding femto nodes;

FIG. 11 is a simplified diagram illustrating coverage areas for wirelesscommunication;

FIG. 12 is a simplified block diagram of several sample aspects ofcommunication components; and

FIGS. 13-17 are simplified block diagrams of several sample aspects ofapparatuses configured to provide transmit power control as taughtherein.

In accordance with common practice the various features illustrated inthe drawings may not be drawn to scale. Accordingly, the dimensions ofthe various features may be arbitrarily expanded or reduced for clarity.In addition, some of the drawings may be simplified for clarity. Thus,the drawings may not depict all of the components of a given apparatus(e.g., device) or method. Finally, like reference numerals may be usedto denote like features throughout the specification and figures.

DETAILED DESCRIPTION

Various aspects of the disclosure are described below. It should beapparent that the teachings herein may be embodied in a wide variety offorms and that any specific structure, function, or both being disclosedherein is merely representative. Based on the teachings herein oneskilled in the art should appreciate that an aspect disclosed herein maybe implemented independently of any other aspects and that two or moreof these aspects may be combined in various ways. For example, anapparatus may be implemented or a method may be practiced using anynumber of the aspects set forth herein. In addition, such an apparatusmay be implemented or such a method may be practiced using otherstructure, functionality, or structure and functionality in addition toor other than one or more of the aspects set forth herein. Furthermore,an aspect may comprise at least one element of a claim.

FIG. 1 illustrates several nodes of a sample communication system 100(e.g., a portion of a communication network). For illustration purposes,various aspects of the disclosure will be described in the context ofone or more access terminals, access points, and network entities thatcommunicate with one another. It should be appreciated, however, thatthe teachings herein may be applicable to other types of apparatuses orother similar apparatuses that are referenced using other terminology.For example, in various implementations access points may be referred toor implemented as base stations, macro cells, femto cells, NodeBs, andso on, while access terminals may be referred to or implemented as userequipment, mobiles, and so on.

Access points in the system 100 provide one or more services (e.g.,network connectivity) for one or more wireless terminals (e.g., accessterminal 102) that may be installed within or that may roam throughout acoverage area of the system 100. For example, at various points in timethe access terminal 102 may connect to an access point 104, an accesspoint 106, or some other access point in the system 100 (not shown).Each of the access points may communicate with one or more networkentities (represented, for convenience, by the network entity 108) tofacilitate wide area network connectivity. A network entity may takevarious forms such as, for example, one or more radio and/or corenetwork entities. Thus, in various implementations the network entity108 may represent functionality such as at least one of: networkmanagement (e.g., via an operation, administration, management, andprovisioning entity), call control, session management, mobilitymanagement, gateway functions, interworking functions, or some othersuitable network functionality.

In accordance with the teachings herein, the access point 106 (e.g., afemto cell) may employ a multi-level power scheme whereby differenttransmit power levels are used at different times. For example, theaccess point may transmit at one power level to provide standardcoverage as represented in a simplified manner by the correspondingdashed line. In addition, the access point may transmit at a higherpower level to provide burst coverage as represented in a simplifiedmanner by the corresponding dashed line.

For purposes of illustration, various aspects of FIG. 1 are not drawn toscale. For example, the standard coverage and burst coverage are notdrawn to scale and are represented as simple circles in FIG. 1. Itshould be appreciated that in practice such coverage would be morecomplex in shape and that the burst coverage may be significantly widerthan the standard coverage. In addition, the distances between theentities of FIG. 1 are not drawn to scale.

The access point 106 may employ the multi-level power scheme for normaltransmissions (e.g., data transmissions on a femto channel) and forbeacon transmissions (e.g., beacon transmission on a macro channel). Forexample, the access point 106 may normally transmit on a given channelat a certain power level, then occasionally transmit at a higher powerlevel (i.e., transmit bursts). In addition, the access point 106 maynormally transmit beacons on one or more macro channels at a certainpower level, then occasionally transmit beacons at a higher power levelon those channels (i.e., transmit beacon bursts).

The access point 106 may set its transmit power levels based on one ormore parameters received from the network. For example, a transmit powercontroller 110 of the access point 106 may define a standard transmitpower level based on a parameter 112 received via the backhaul (e.g.,received from the access point 104 via the network entity 108). Inaddition, the transmit power controller 110 may define a beacon transmitpower level and/or a beacon burst transmit power level based on one ormore parameters 114 received over-the-air from the access point 104(e.g., from a macro access point within the coverage of which the accesspoint 106 lies).

As a specific example, the power levels of regular femto celltransmission, regular beacon, beacon burst, and femto cell burst may becalibrated based on measurements of macro signal strength and totalreceived signal power. The regular beacon power is set such that a fixed(small) outage radius is created. If the network operator has set theparameter Sintersearch>0 for the macro cells, then the beacon coverageradius (radius at which an inter-frequency search is triggered) will belarger than the outage radius. The beacon burst power is set based onthe macro cell Sintersearch parameter to maintain a consistenttriggering of inter-frequency cell search at the femto cell deploymentlocation boundary (e.g., apartment, home, or office boundary),regardless of the location of the femto cell within the macro cell. Thefemto cell power is set based on the Qqualmin parameter broadcast by themacro network on system information block (SIB) 11 for that femto cellpilot scrambling code (PSC), such that an access terminal within theboundary of the apartment/home/office will have sufficient femto cellcoverage to be able to reselect to the femto cell. In this way,consistent discovery of the femto cell by home access terminals (e.g.,access terminals that belong to the whitelist of the femto cell)arriving home may be ensured, whilst minimizing outage to macro accessterminals (e.g., access terminals that do not belong to that whitelist),regardless of the location of the femto cell within the macro cell.

The teachings herein may be used in a variety of deployment schemes. Forexample, the teachings herein may be used in a co-channel deploymentscheme where a macro access point and a femto access point operate onthe same channel (e.g., frequency f1), and where at least one macroaccess point operates on one or more other channels (e.g., frequencyf2). The teachings herein also may be used in a dedicated channeldeployment scheme where a femto access point operates on one channel(e.g., frequency f1) and one or more macro access points operate on oneor more other channels (e.g., frequency f2). For purposes ofillustration, the discussion that follows primarily describes aco-channel deployment scheme.

In some aspects, the term “channel: as used herein refers to aparticular frequency band (e.g., corresponding to a designated nominalfrequency) allocated by the network. Conventionally such a channel maybe referred to as a frequency. For example, the channel on which a femtocell operates may be referred to as the femto frequency, while thechannel on which a macro cell operates may be referred to as the macrofrequency.

Sample operations that may be perform by an access point such as theaccess point 106 will now be described in more detail in conjunctionwith the flowcharts of FIGS. 2 and 4-7. For convenience, the operationsof FIGS. 2 and 4-7 (or any other operations discussed or taught herein)may be described as being performed by specific components (e.g., thecomponents of FIG. 1 or FIG. 8). It should be appreciated, however, thatthese operations may be performed by other types of components and maybe performed using a different number of components. It also should beappreciated that one or more of the operations described herein may notbe employed in a given implementation.

FIG. 2 describes sample operations that may be performed in conjunctionwith an access point providing synchronized burst transmissions.Initially, standard and burst power levels are defined for normaltransmissions and beacon transmission. Then, the access pointsynchronizes the transmissions of the bursts.

For purposes of illustration the operations of FIG. 2 will be describedin the context of a femto cell (i.e., a femto access point). In someaspects, femto cell power calibration (e.g., setting the femto transmitpower on the femto frequency f1) is designed to provide adequate femtocell coverage for home access terminals whilst at the same time limitinginterference to, and reselection attempts by, macro access terminalsthat may be situated just outside the coverage radius of the femto cell.In addition, beacon power calibration (e.g., setting the jamming beacontransmit power on the macro frequency f2) is designed to both facilitatediscovery of the femto cell by home access terminals, and preventdiscovery of the femto cell by macro access terminals in the vicinity ofthe femto cell.

In the example that follows, power calibration consists of computingfour values: 1) femto cell transmit power on f1; 2) femto cell burstpower on f1; 3) beacon power on f2; and 4) beacon burst power on f2.Both the beacon and femto transmit powers undergo periodic, momentarybursts, according to a defined burst period where each burst lasts adefined burst duration. As discussed in herein, through the use of suchbursts, a home access terminal may more readily discover its associatedfemto cell. The beacon and femto burst are synchronized to occur at thesame time and have the same duration. As discussed in more detail below,in some implementations the bursts are time-synchronized across thenetwork (i.e., among other access points). In this way, a given accessterminal may respond only to the burst emanating from the femto cellnearest that access terminal.

The burst period may be defined in various ways. In some implementationsthe burst period is selected as follows: burstduration=N×DRX_cycle_duration, where N is the number of consecutive DRXcycles that the reselection criteria need to be satisfied for, in orderfor cell reselection to take place, as given by the Treselectionparameter of the strongest serving macro cell (e.g., as seen at thefemto cell). In a sample implementation, a burst duration on the orderof 1-2 minutes is used.

Referring to FIG. 2, as represented at block 202, at some point in timeaccess point transmit power is defined. For example, a femto cell maydetermine the power at which it will normally transmit on the femtofrequency (e.g., frequency f1). Linear units are used in the equationsthat follow.

The femto cell computes an estimate of the total received signal powerfrom macro cells (e.g., excluding contributions from other femto cells),on the femto cell frequency f1 according to the following equation:

${{Io\_ macro}{\_ f1}} = \frac{\sum\limits_{i \in {{{macro}\_ {PSC}}{\_ {lis}t}{\_ f1}}}\; {{Ecp\_ macro}{\_ f1}(i)}}{{Ecp}/{Ior\_ macro}}$

Here, macro_PSC_list_f1 is the list of macro PSCs on f1, Ecp_macro_f1(i)is the received pilot energy of the i^(th) macro PSC on f1, andEcp/Ior_macro is a parameter corresponding to the estimated ratio ofpilot power to total power for macro cells. The femto cell computes thetransmit power according to the following equations:

$\mspace{79mu} {{P\_ femto1} = {\left( {\frac{{Ecp\_ macro}{\_ f1}}{{Ecp}/{Io\_ min}} - {{Io\_ macro}{\_ f1}}} \right) \cdot {PL\_ edge}}}$${P\_ femto2} = {{\frac{Qqualmin\_ femto}{{pilot\_ gain} - {Qqualmin\_ femto}} \cdot {Io\_ macro}}{{\_ f1} \cdot {PL\_ edge}}}$     P_femto3 = min (P_femto1, P_femto2)     P_femto = max (P_femto_min, min (P_femto3, P_max))

Here, Ecp_macro_f1 is the received pilot energy of the strongest macroPSC on f1, Ecp/Io_min is a parameter indicative of the minimum channelquality required for a macro cell user, PL_edge is a parameterrepresenting the boundary of femto cell coverage, Qqualmin_femto is theQqualmin value for the femto cell PSC read from SIB 11 of the macro cellon f1, pilot_gain is a parameter representing the fraction of themaximum total transmitted femto cell power attributed to the pilotchannel, P_femto_min is a parameter corresponding to the minimum (fullyloaded) femto cell transmit power, and P_max is a parametercorresponding to the maximum femto cell transmit power.

The power setting P_femto2 relates to preventing access terminalsfurther than PL_edge away from the femto cell from reselecting to thefemto cell. This limits the number of reselection attempts by accessterminals that are not authorized at that femto cell (e.g., attempts bymacro access terminals), and thus improves the standby time of legacyaccess terminals. The power setting P_femto1 relates to protecting macroaccess terminals on the same frequency as the femto cell by limiting thetransmit power such that when an access terminal is further than PL_edgeaway from the femto cell, the access terminal hears the macro at anEcp/Io of roughly Ecp/Io_min. Here, it should be appreciated that amismatch between the Ecp_macro and Io_macro values at the femto cellversus at the macro access terminal may lead to degradation in Ecp/Io.Also, the presence of an additional interfering femto cell locatedfurther than PL_edge from the macro access terminal may lower Ecp/Io by,for example, as much as 3 dB in a worst case scenario. For this reason,the Ecp/Io_min parameter may be set a few dB higher than the Qqualminvalue.

Referring again to FIG. 2, as represented at block 204, the access pointburst transmit power is defined once the access point transmit power isdefined. For example, a femto cell may determine the power at which itwill transmit bursts on the femto frequency by adding a margin to thefemto power calculated at block 202 as follows:

P_femto_burst1=P_femto3·femto_burst_margin

P_femto_burst=max(P_femto_min,min(P_femto_burst1,P_max))

As represented at block 206, the beacon transmit power is defined. Here,a femto cell may determine the standard power level at which it willpredominantly transmit beacons on a macro frequency (e.g., frequencyf2). As an example, the beacon power may be computed according to thefollowing equations:

${Io\_ beacon} = {{Io\_ f2} + \frac{\max \left( {{{P\_ fempto}/{ACIR}},{P\_ NF}} \right)}{PL\_ BE}}$${P\_ beacon1} = {\left( {\frac{{Ecp\_ macro}{\_ f2}}{Qqualmin} - {Io\_ beacon}} \right) \cdot {PL\_ BE}}$P_beacon2 = min (P_beacon1, P_max)${P\_ beacon} = \left\{ \begin{matrix}{P\_ beacon2} & {{{if}\mspace{14mu} {P\_ beacon2}} \geq {{P\_ beacon}{\_ min}}} \\0 & {otherwise}\end{matrix} \right.$

Here, Io_f2 is the total received signal power measured on frequency f2.ACIR is a parameter corresponding to the adjacent carrier interferenceratio, P_NF is a parameter corresponding to the received power of thenoise floor of the emission mask, PL_BE is a parameter representing thepath loss from the femto cell at which the beacon will likely causemacro Ecp/Io to fall below Qqualmin, Ecp_macro_f2 is the received pilotenergy of the strongest macro PSC on f2, Qqualmin is the correspondingvalue for the strongest macro cell PSC on f2 read from SIB 3, andP_beacon_min is a parameter corresponding to the minimum beacon transmitpower.

As represented at block 208 of FIG. 2, the beacon burst transmit poweris defined. For example, a femto cell may determine the power at whichit will transmit beacon bursts on a macro frequency based on thefollowing equations:

${{P\_ beacon}{\_ burst1}} = {\left( {\frac{{Ecp\_ macro}{\_ f2}}{{{Qqualmin} \cdot {Sintersearch} \cdot {beacon\_ burst}}{\_ margin}} - {Io\_ f2}} \right) \cdot {PL\_ edge}}$  P_beacon_burst2 = min (P_beacon_burst1_P_max)${{P\_ beacon}{\_ burst}} = \left\{ \begin{matrix}{{P\_ beacon}{\_ burst2}} & {{{if}\mspace{14mu} {P\_ beacon}{\_ burst2}} \geq {{P\_ beacon}{\_ min}}} \\0 & {otherwise}\end{matrix} \right.$

Here, Sintersearch is the corresponding value from SIB 3 of thestrongest macro cell on f2. The beacon burst power is chosen differentlyto the regular beacon power in this example. Specifically, it is set totrigger an inter-frequency search for access terminals closer thanPL_edge from the femto cell. From the above, it is seen that the beaconburst power is set as a function of the network operator's macro cellSintersearch parameter. This helps to ensures consistent home accessterminal discovery of its femto cell at the apartment/house/officeboundary, regardless of the macro cell Sintersearch setting. In otherwords, the beacon burst boundary for a given femto cell may remainsubstantially constant even if the network changes the value ofSintersearch.

In the above equations, the beacon power is chosen such that macroaccess terminals further than PL_BE from the femto cell will not be inmacro outage (macro Ecp/Io>Qqualmin). In this example, if the macrosignal strength is sufficiently poor to begin with, the beacon isswitched off to prevent further degradation of macro coverage. The pathloss at which the beacon will trigger an inter-frequency search dependson the network's Sintersearch setting, but will be greater than PL_BEprovided Sintersearch>0.

FIG. 3 illustrates this concept in a simplified manner for an accesspoint 304 deployed in a building 302 (shown in plan view). Here, theboundary of the outage region is represented by the dashed line 306,while the boundary of the beacon coverage region is represented by thedashed line 308.

As mentioned above, in some implementations, the transmission of burstsmay be synchronized among multiple access points. For example, a set offemto cells (e.g., all femto cells within a given network or within thecoverage of a given macro cell) may synchronize their bursttransmissions. Accordingly, as represented by block 210 of FIG. 2, agiven access point may optionally determine the burst timing used by atleast one other access point.

As represented at block 212, the access point synchronizes its bursttransmissions. For example, a femto cell may transmit its femto burstsand its beacon burst at substantially the same time. That is, the burstsare transmitted with a common (i.e., substantially the same) periodicityand with a common burst duration. In addition, as discussed above, insome implementations the access point may synchronize the timing of itsburst transmissions with the timing of burst transmissions by at leastone other access point.

For purposes of illustration, an example of parameters settings (in dBunits) that may be employed in conjunction with the equations describedabove follows: Ecp/Ior_macro=−7 dB, Ecp/Io_min=−16 dB,Qqualmin_femto=−12 dB, Qqualmin=−18 dB, femto_burst_margin=10 dB,beacon_burst_margin=−8 dB, PL_BE=45 dB for apartments, 55 dB for houses,65 dB for office buildings, PL_edge=75 dB for apartments, 85 dB forhouses, 95 dB for office buildings, P_femto_min=−30 dBm,P_beacon_min=−40 dBm, P_max=10 dBm, P_NF=−45 dBm, ACIR=33 dB,pilot_gain=−10 dB.

Referring now to FIG. 4, sample operations that may be performed by anaccess point in conjunction with defining beacon power based on one ormore parameters that are received over-the-air by an access point aredescribed. These operations are applicable to standard beacon powerand/or beacon burst power.

As represented by block 402, the access point receives an RF signal thatincludes one or more parameters. For example, a femto cell may receive asignal broadcast by a macro access point (e.g., sent by the strongestmacro cell from the perspective of the femto cell) on a macro frequency(e.g., frequency f2).

In some cases, the parameter may comprise a minimum required signalquality parameter such as a Qqualmin parameter (e.g., received via amessage including SIB 3). In some aspects, a quality parameter such asthis may specify a minimum signal quality for an access terminal tosustain a call with an access point (e.g., the macro access point thatis broadcasting the parameter).

In some cases the parameter may comprise a search parameter such as anSintersearch parameter. In some aspects, a search parameter such as thismay comprise a value that is defined to control how (e.g., howaggressively) an access terminal searches for other cells.

As represented by block 404, the access point determines beacon transmitpower based on the received parameter(s).

For example, a femto cell may compute the standard beacon transmit powerbased on Qqualmin as discussed above at FIG. 2. Also as discussed above,the computation of the standard beacon transmit power may be based onother parameters such as a defined path loss target (e.g., PL_BE). Insome aspects, a path loss target such as this may correspond to anoutage region within which transmission of a beacon by the access pointcauses call drops for an access terminal (e.g., a macro accessterminal), and outside of which transmission of a beacon by the accesspoint does not cause call drops for the access terminal.

As another example, a femto cell may compute the beacon burst transmitpower based on Sintersearch as discussed above at FIG. 2. Also asdiscussed above, the computation of the beacon burst transmit power maybe based on other parameters such as a defined path loss target (e.g.,PL_edge). In some aspects, the determination of the beacon bursttransmit power comprises providing a transmit power that results in asearch for other cells being triggered at an access terminal if theaccess terminal is closer than this defined path loss target to theaccess point.

As represented by block 406, the access point transmits a beacon signalbased on the determined beacon transmit power. As discussed herein, theaccess point may transmit a beacon at the standard beacon transmit powerlevel, with beacon bursts being provided at the beacon burst transmitpower level. In the co-channel deployment example described above, theaccess point may thus transmit the beacon on the macro frequency f2.

FIG. 5 describes sample operations that may be performed in conjunctionwith defining beacon power based on total received signal power and adefined outage radius parameter.

As represented by block 502, the access point receives RF signals on aradio channel. For example, a femto cell may receive signals broadcastby access points on a macro frequency (e.g., frequency f2).

As represented by block 504, the access point determines the totalreceived signal power associated with the radio channel. This signalpower may be based on signals received from multiple macro cells (i.e.,not just the strongest macro cell) and from one or more femto cells (orother types of cells operating on the channel). In the example of FIG.2, this value is designated as Io_f2.

As represented by block 506, the access point determines the beacontransmit power based on the total received signal power (e.g., Io_f2)and a defined outage radius parameter (e.g., PL_BE) as discussed aboveat FIG. 2. It should be appreciated that the term “radius” here isrepresentative of a distance (e.g., an approximate or average distance)from the access point. The use of this term does not infer that thecoverage necessarily comprises a circle. As discussed above, thecomputation of the beacon transmit power may be based on otherparameters such as Qqualmin.

The defined outage radius parameter may comprise a defined path losstarget as discussed above. In some cases this path loss may be definedbased on the deployment (e.g., the location) of the access point. Forexample, a larger path loss may be defined if the access point is beingdeployed in a larger building. As a specific example, a larger path lossmay be defined for an access point deployed in a house as opposed to anaccess point deployed in a smaller apartment.

As represented by block 508, the access point transmits the beacon basedon the beacon transmit power determined at block 506 (except when beaconbursts are being transmitted). In the co-channel deployment exampledescribed above, the access point may thus transmit the beacon on themacro frequency f2.

FIG. 6 describes sample operations that may be performed in conjunctionwith defining access point power (e.g., femto cell transmit power) basedon a minimum required signal quality parameter (e.g., Qqualmin).

As represented by block 602, the access point receives a minimumrequired signal quality parameter defined for the access point such as aQqualmin parameter. In some aspects, a quality parameter such as thismay specify the minimum signal quality required at an access terminalfor the access terminal to reselect to the access point (e.g., toreselect to the femto cell). In some cases, an access point may receivethis parameter via the backhaul. For example, a femto cell may receivethe parameter via a message that includes SIB 11 that is sent by a macroaccess point (e.g., the strongest macro cell currently seen by the femtocell). In the example of FIG. 2, this quality parameter is referred toas Qqualmin_femto.

As represented by block 604, the access point determines the accesspoint transmit power based on the received minimum required signalquality parameter. As discussed above at FIG. 2, the computation of thistransmit power may be based on other parameters such as a definedcoverage parameter (e.g., PL_edge), the received pilot energy from thestrongest macro access point on the femto frequency (e.g.,Ecp_macro_f1), and the received energy on the femto frequency fromaccess points of a defined type (e.g., Io_macro_f1). An example of howthe latter parameter may be acquired is described in more detail belowat FIG. 7.

As represented by block 606, the access point determines access pointburst transmit power based on the access point transmit power. Forexample, a defined margin may be added to the access point transmitpower determined at block 604.

As represented by block 608, the access point transmits signals based onthe access point transmit power and the access point burst transmitpower. In the co-channel deployment example described above, the accesspoint transmits these signals on the femto frequency f1.

FIG. 7 describes sample operations that may be performed in conjunctionwith defining access point power (e.g., femto cell transmit power) basedon the received energy on a channel from access points of a defined typeand based on a defined coverage parameter.

As represented by block 702, the access point receives RF signals on aradio channel. For example, a femto cell may receive signals broadcastby access points on the femto frequency (e.g., frequency f1).

As represented by block 704, the access point identifies the receivedsignals that were sent by access points of a defined type (e.g., macroaccess points). Then, as represented by block 706, the access pointdetermines the received energy associated with the identified signals(i.e., the received energy on the channel solely from the macro accesspoints). In the example of FIG. 2, this quantity is referred to asIo_macro_f1.

As represented by block 708, the access point determines the accesspoint transmit power based on the received energy and a defined coverageparameter (e.g., PL_edge) as discussed above at FIG. 2. Also asdiscussed above, the computation of this transmit power may be based onother parameters such as Qqualmin_femto and the received pilot energy(e.g., Ecp_macro_f1) from the strongest macro access point on the femtofrequency (e.g., determined based on the signals identified at block704).

As represented by blocks 710 and 712, the access point determines accesspoint burst transmit power based on the access point transmit power, andtransmits signals based on the access point transmit power and theaccess point burst transmit power. Again, the access point may transmitthese signals on the femto frequency f1.

As mentioned above, the teachings herein are applicable to a dedicatedchannel deployment. As an example, in such a case, a femto cell signalmay be transmitted on frequency f1 and a beacon transmitted on frequencyf2. In this case, the beacon power and the beacon burst power may becalculated in the same manner as described above for the co-channeldeployment scenario.

However, the power settings for the femto cell transmit power may besimplified since there is no macro on the femto frequency f1. Forexample, the femto cell transmit power may be calculate according to thefollowing equations:

${P\_ femto1} = \frac{{PL\_ edge} \cdot {Qqualmin\_ femto} \cdot {No}}{pilot\_ gain}$P_femto = max (P_femto_min, min (P_femto1, P_max))

Here, No is a parameter representing the thermal noise level at theaccess terminal. This value is chosen such that an access terminal thatis PL_edge from the femto cell will experience a femto Ecp/Io ofQqualmin_femto, in the absence of other, interfering femto cells.

The femto cell burst power is then set in a similar manner as above:

P_femto_burst1=P_femto1·femto_burst_margin

P_femto_burst=max(P_femto_min,min(P_femto_burst1,P_max))

Also, in a sample implementation, the same parameters settings as theco-channel deployment case may be used, with P_femto_min=−30 dBm andNo=−99 dBm. These parameter settings may thus lead to the followingvalues for femto cell transmit power:

Femto cell Femto cell burst Deployment Type power (dBm) power (dBm)Apartment (PL_edge = 75 dB) −26 −16 House (PL_edge = 85 dB) −16 −6Office Building (PL_edge = 95 dB) −6 +4

FIG. 8 illustrates several sample components that may be incorporatedinto an access point 802 (e.g., corresponding to the access point 106)to perform power control operations as taught herein. In practice, thedescribed components also may be incorporated into other nodes in acommunication system. For example, other nodes in a system may includecomponents similar to those described for the access point 802 toprovide similar functionality. Also, a given node may contain one ormore of the described components. For example, an access point maycontain multiple transceiver components that enable the access point tooperate on multiple frequencies and/or communicate via differenttechnologies.

As shown in FIG. 8, the access point 802 includes a transceiver 804 forcommunicating with other nodes. The transceiver 804 includes atransmitter 806 for sending signals (e.g., transmitting femto signals,femto burst signals, beacon signals, and beacon burst signals, andsynchronizing the timing of burst transmissions) and a receiver 808 forreceiving signals (e.g., receiving RF signals and parameters). Theaccess point 802 includes a network interface 810 for communicating withother nodes (e.g., other network nodes). For example, the networkinterface 810 may be configured to communicate with one or more networknodes via a wire-based or wireless backhaul. In some aspects, thenetwork interface 810 may be implemented as a transceiver (e.g.,including transmitter and receiver components) configured to supportwire-based or wireless communication (e.g., receiving parameters overthe backhaul). The access point 802 also includes a transmit powercontroller 812 (e.g., corresponding to the controller 110) forperforming power control-related operations (e.g., determining beacontransmit power, determining total received signal power, determiningbeacon transmit power, defining access point transmit power, definingaccess point burst transmit power, defining beacon transmit power,defining beacon burst transmit power, determining transmit power,identifying signals, determining received energy, determining receivedpilot energy) and other similar operations as taught herein.

In some implementations the components of FIG. 8 may be implemented inone or more processors (e.g., that uses and/or incorporates data memoryfor storing information or code used by the processor(s) to provide thisfunctionality). For example, the functionality of blocks 810 and 812(and, optionally, some of the functionality of the transceiver 804) maybe implemented by a processor or processors of an access point and datamemory of the access point (e.g., by execution of appropriate codeand/or by appropriate configuration of processor components).

As discussed above, in some aspects the teachings herein may be employedin a network that includes macro scale coverage (e.g., a large areacellular network such as a 3G network, typically referred to as a macrocell network or a WAN) and smaller scale coverage (e.g., aresidence-based or building-based network environment, typicallyreferred to as a LAN). As an access terminal (AT) moves through such anetwork, the access terminal may be served in certain locations byaccess points that provide macro coverage while the access terminal maybe served at other locations by access points that provide smaller scalecoverage. In some aspects, the smaller coverage nodes may be used toprovide incremental capacity growth, in-building coverage, and differentservices (e.g., for a more robust user experience).

In the description herein, a node (e.g., an access point) that providescoverage over a relatively large area may be referred to as a macroaccess point while a node that provides coverage over a relatively smallarea (e.g., a residence) may be referred to as a femto access point(e.g., referred to above as a femto cell). It should be appreciated thatthe teachings herein may be applicable to nodes associated with othertypes of coverage areas. For example, a pico access point may providecoverage (e.g., coverage within a commercial building) over an area thatis smaller than a macro area and larger than a femto area. In variousapplications, other terminology may be used to reference a macro accesspoint, a femto access point, or other access point-type nodes. Forexample, a macro access point may be configured or referred to as anaccess node, base station, access point, eNodeB, macro cell, and so on.Also, a femto access point may be configured or referred to as a HomeNodeB, Home eNodeB, access point base station, femto cell, and so on. Insome implementations, a node may be associated with (e.g., referred toas or divided into) one or more cells or sectors. A cell or sectorassociated with a macro access point, a femto access point, or a picoaccess point may be referred to as a macro cell, a femto cell, or a picocell, respectively.

FIG. 9 illustrates a wireless communication system 900, configured tosupport a number of users, in which the teachings herein may beimplemented. The system 900 provides communication for multiple cells902, such as, for example, macro cells 902A-902G, with each cell beingserviced by a corresponding access point 904 (e.g., access points904A-904G). As shown in FIG. 9, access terminals 906 (e.g., accessterminals 906A-906L) may be dispersed at various locations throughoutthe system over time. Each access terminal 906 may communicate with oneor more access points 904 on a forward link (FL) and/or a reverse link(RL) at a given moment, depending upon whether the access terminal 906is active and whether it is in soft handoff, for example. The wirelesscommunication system 900 may provide service over a large geographicregion. For example, macro cells 902A-902G may cover a few blocks in aneighborhood or several miles in rural environment.

FIG. 10 illustrates an exemplary communication system 1000 where one ormore femto access points are deployed within a network environment.Specifically, the system 1000 includes multiple femto access points 1010(e.g., femto access points 1010A and 1010B) installed in a relativelysmall scale network environment (e.g., in one or more user residences1030). Each femto access point 1010 may be coupled to a wide areanetwork 1040 (e.g., the Internet) and a mobile operator core network1050 via a DSL router, a cable modem, a wireless link, or otherconnectivity means (not shown). As will be discussed below, each femtoaccess point 1010 may be configured to serve associated access terminals1020 (e.g., access terminal 1020A) and, optionally, other (e.g., hybridor alien) access terminals 1020 (e.g., access terminal 1020B). In otherwords, access to femto access points 1010 may be restricted whereby agiven access terminal 1020 may be served by a set of designated (e.g.,home) femto access point(s) 1010 but may not be served by anynon-designated femto access points 1010 (e.g., a neighbor's femto accesspoint 1010).

FIG. 11 illustrates an example of a coverage map 1100 where severaltracking areas 1102 (or routing areas or location areas) are defined,each of which includes several macro coverage areas 1104. Here, areas ofcoverage associated with tracking areas 1102A, 1102B, and 1102C aredelineated by the wide lines and the macro coverage areas 1104 arerepresented by the larger hexagons. The tracking areas 1102 also includefemto coverage areas 1106. In this example, each of the femto coverageareas 1106 (e.g., femto coverage areas 1106B and 1106C) is depictedwithin one or more macro coverage areas 1104 (e.g., macro coverage areas1104A and 1104B). It should be appreciated, however, that some or all ofa femto coverage area 1106 may not lie within a macro coverage area1104. In practice, a large number of femto coverage areas 1106 (e.g.,femto coverage areas 1106A and 1106D) may be defined within a giventracking area 1102 or macro coverage area 1104. Also, one or more picocoverage areas (not shown) may be defined within a given tracking area1102 or macro coverage area 1104.

Referring again to FIG. 10, the owner of a femto access point 1010 maysubscribe to mobile service, such as, for example, 3G mobile service,offered through the mobile operator core network 1050. In addition, anaccess terminal 1020 may be capable of operating both in macroenvironments and in smaller scale (e.g., residential) networkenvironments. In other words, depending on the current location of theaccess terminal 1020, the access terminal 1020 may be served by a macrocell access point 1060 associated with the mobile operator core network1050 or by any one of a set of femto access points 1010 (e.g., the femtoaccess points 1010A and 1010B that reside within a corresponding userresidence 1030). For example, when a subscriber is outside his home, heis served by a standard macro access point (e.g., access point 1060) andwhen the subscriber is at home, he is served by a femto access point(e.g., access point 1010A). Here, a femto access point 1010 may bebackward compatible with legacy access terminals 1020.

A femto access point 1010 may be deployed on a single frequency or, inthe alternative, on multiple frequencies. Depending on the particularconfiguration, the single frequency or one or more of the multiplefrequencies may overlap with one or more frequencies used by a macroaccess point (e.g., access point 1060).

In some aspects, an access terminal 1020 may be configured to connect toa preferred femto access point (e.g., the home femto access point of theaccess terminal 1020) whenever such connectivity is possible. Forexample, whenever the access terminal 1020A is within the user'sresidence 1030, it may be desired that the access terminal 1020Acommunicate only with the home femto access point 1010A or 1010B.

In some aspects, if the access terminal 1020 operates within the macrocellular network 1050 but is not residing on its most preferred network(e.g., as defined in a preferred roaming list), the access terminal 1020may continue to search for the most preferred network (e.g., thepreferred femto access point 1010) using a better system reselection(BSR) procedure, which may involve a periodic scanning of availablesystems to determine whether better systems are currently available andsubsequently acquire such preferred systems. The access terminal 1020may limit the search for specific band and channel. For example, one ormore femto channels may be defined whereby all femto access points (orall restricted femto access points) in a region operate on the femtochannel(s). The search for the most preferred system may be repeatedperiodically. Upon discovery of a preferred femto access point 1010, theaccess terminal 1020 selects the femto access point 1010 and registerson it for use when within its coverage area.

Access to a femto access point may be restricted in some aspects. Forexample, a given femto access point may only provide certain services tocertain access terminals. In deployments with so-called restricted (orclosed) access, a given access terminal may only be served by the macrocell mobile network and a defined set of femto access points (e.g., thefemto access points 1010 that reside within the corresponding userresidence 1030). In some implementations, an access point may berestricted to not provide, for at least one node (e.g., accessterminal), at least one of: signaling, data access, registration,paging, or service.

In some aspects, a restricted femto access point (which may also bereferred to as a Closed Subscriber Group Home NodeB) is one thatprovides service to a restricted provisioned set of access terminals.This set may be temporarily or permanently extended as necessary. Insome aspects, a Closed Subscriber Group (CSG) may be defined as the setof access points (e.g., femto access points) that share a common accesscontrol list of access terminals.

Various relationships may thus exist between a given femto access pointand a given access terminal. For example, from the perspective of anaccess terminal, an open femto access point may refer to a femto accesspoint with unrestricted access (e.g., the femto access point allowsaccess to any access terminal). A restricted femto access point mayrefer to a femto access point that is restricted in some manner (e.g.,restricted for access and/or registration). A home femto access pointmay refer to a femto access point on which the access terminal isauthorized to access and operate on (e.g., permanent access is providedfor a defined set of one or more access terminals). A hybrid (or guest)femto access point may refer to a femto access point on which differentaccess terminals are provided different levels of service (e.g., someaccess terminals may be allowed partial and/or temporary access whileother access terminals may be allowed full access). An alien femtoaccess point may refer to a femto access point on which the accessterminal is not authorized to access or operate on, except for perhapsemergency situations (e.g., 911 calls).

From a restricted femto access point perspective, a home access terminalmay refer to an access terminal that is authorized to access therestricted femto access point installed in the residence of that accessterminal's owner (usually the home access terminal has permanent accessto that femto access point). A guest access terminal may refer to anaccess terminal with temporary access to the restricted femto accesspoint (e.g., limited based on deadline, time of use, bytes, connectioncount, or some other criterion or criteria). An alien access terminalmay refer to an access terminal that does not have permission to accessthe restricted femto access point, except for perhaps emergencysituations, for example, such as 911 calls (e.g., an access terminalthat does not have the credentials or permission to register with therestricted femto access point).

For convenience, the disclosure herein describes various functionalityin the context of a femto access point. It should be appreciated,however, that a pico access point may provide the same or similarfunctionality for a larger coverage area. For example, a pico accesspoint may be restricted, a home pico access point may be defined for agiven access terminal, and so on.

The teachings herein may be employed in a wireless multiple-accesscommunication system that simultaneously supports communication formultiple wireless access terminals. Here, each terminal may communicatewith one or more access points via transmissions on the forward andreverse links. The forward link (or downlink) refers to thecommunication link from the access points to the terminals, and thereverse link (or uplink) refers to the communication link from theterminals to the access points. This communication link may beestablished via a single-in-single-out system, amultiple-in-multiple-out (MIMO) system, or some other type of system.

A MIMO system employs multiple (N_(T)) transmit antennas and multiple(N_(R)) receive antennas for data transmission. A MIMO channel formed bythe N_(T) transmit and N_(R) receive antennas may be decomposed intoN_(S) independent channels, which are also referred to as spatialchannels, where N_(S)≦min{N_(T), N_(R)}. Each of the N_(S) independentchannels corresponds to a dimension. The MIMO system may provideimproved performance (e.g., higher throughput and/or greaterreliability) if the additional dimensionalities created by the multipletransmit and receive antennas are utilized.

A MIMO system may support time division duplex (TDD) and frequencydivision duplex (FDD). In a TDD system, the forward and reverse linktransmissions are on the same frequency region so that the reciprocityprinciple allows the estimation of the forward link channel from thereverse link channel. This enables the access point to extract transmitbeam-forming gain on the forward link when multiple antennas areavailable at the access point.

FIG. 12 illustrates a wireless device 1210 (e.g., an access point) and awireless device 1250 (e.g., an access terminal) of a sample MIMO system1200. At the device 1210, traffic data for a number of data streams isprovided from a data source 1212 to a transmit (TX) data processor 1214.Each data stream may then be transmitted over a respective transmitantenna.

The TX data processor 1214 formats, codes, and interleaves the trafficdata for each data stream based on a particular coding scheme selectedfor that data stream to provide coded data. The coded data for each datastream may be multiplexed with pilot data using OFDM techniques. Thepilot data is typically a known data pattern that is processed in aknown manner and may be used at the receiver system to estimate thechannel response. The multiplexed pilot and coded data for each datastream is then modulated (i.e., symbol mapped) based on a particularmodulation scheme (e.g., BPSK, QSPK, M-PSK, or M-QAM) selected for thatdata stream to provide modulation symbols. The data rate, coding, andmodulation for each data stream may be determined by instructionsperformed by a processor 1230. A data memory 1232 may store programcode, data, and other information used by the processor 1230 or othercomponents of the device 1210.

The modulation symbols for all data streams are then provided to a TXMIMO processor 1220, which may further process the modulation symbols(e.g., for OFDM). The TX MIMO processor 1220 then provides N_(T)modulation symbol streams to N_(T) transceivers (XCVR) 1222A through1222T. In some aspects, the TX MIMO processor 1220 applies beam-formingweights to the symbols of the data streams and to the antenna from whichthe symbol is being transmitted.

Each transceiver 1222 receives and processes a respective symbol streamto provide one or more analog signals, and further conditions (e.g.,amplifies, filters, and upconverts) the analog signals to provide amodulated signal suitable for transmission over the MIMO channel. N_(T)modulated signals from transceivers 1222A through 1222T are thentransmitted from N_(T) antennas 1224A through 1224T, respectively.

At the device 1250, the transmitted modulated signals are received byN_(R) antennas 1252A through 1252R and the received signal from eachantenna 1252 is provided to a respective transceiver (XCVR) 1254Athrough 1254R. Each transceiver 1254 conditions (e.g., filters,amplifies, and downconverts) a respective received signal, digitizes theconditioned signal to provide samples, and further processes the samplesto provide a corresponding “received” symbol stream.

A receive (RX) data processor 1260 then receives and processes the N_(R)received symbol streams from N_(R) transceivers 1254 based on aparticular receiver processing technique to provide N_(T) “detected”symbol streams. The RX data processor 1260 then demodulates,deinterleaves, and decodes each detected symbol stream to recover thetraffic data for the data stream. The processing by the RX dataprocessor 1260 is complementary to that performed by the TX MIMOprocessor 1220 and the TX data processor 1214 at the device 1210.

A processor 1270 periodically determines which pre-coding matrix to use(discussed below). The processor 1270 formulates a reverse link messagecomprising a matrix index portion and a rank value portion. A datamemory 1272 may store program code, data, and other information used bythe processor 1270 or other components of the device 1250.

The reverse link message may comprise various types of informationregarding the communication link and/or the received data stream. Thereverse link message is then processed by a TX data processor 1238,which also receives traffic data for a number of data streams from adata source 1236, modulated by a modulator 1280, conditioned by thetransceivers 1254A through 1254R, and transmitted back to the device1210.

At the device 1210, the modulated signals from the device 1250 arereceived by the antennas 1224, conditioned by the transceivers 1222,demodulated by a demodulator (DEMOD) 1240, and processed by a RX dataprocessor 1242 to extract the reverse link message transmitted by thedevice 1250. The processor 1230 then determines which pre-coding matrixto use for determining the beam-forming weights then processes theextracted message.

FIG. 12 also illustrates that the communication components may includeone or more components that perform power control operations as taughtherein. For example, a power control component 1290 may cooperate withthe processor 1230 and/or other components of the device 1210 to sendsignals to another device (e.g., device 1250) as taught herein. Itshould be appreciated that for each device 1210 and 1250 thefunctionality of two or more of the described components may be providedby a single component. For example, a single processing component mayprovide the functionality of the power control component 1290 and theprocessor 1230.

The teachings herein may be incorporated into various types ofcommunication systems and/or system components. In some aspects, theteachings herein may be employed in a multiple-access system capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., by specifying one or more of bandwidth, transmitpower, coding, interleaving, and so on). For example, the teachingsherein may be applied to any one or combinations of the followingtechnologies: Code Division Multiple Access (CDMA) systems,Multiple-Carrier CDMA (MCCDMA), Wideband CDMA (W-CDMA) systems,Universal Mobile Telecommunication System (UMTS) systems, High-SpeedPacket Access (HSPA, HSPA+) systems, Time Division Multiple Access(TDMA) systems, Frequency Division Multiple Access (FDMA) systems,Single-Carrier FDMA (SC-FDMA) systems, Orthogonal Frequency DivisionMultiple Access (OFDMA) systems, or other multiple access techniques. Awireless communication system employing the teachings herein may bedesigned to implement one or more standards, such as IS-95, cdma2000,IS-856, W-CDMA, TDSCDMA, and other standards. A CDMA network mayimplement a radio technology such as Universal Terrestrial Radio Access(UTRA), cdma2000, or some other technology. UTRA includes W-CDMA and LowChip Rate (LCR). The cdma2000 technology covers IS-2000, IS-95 andIS-856 standards. A TDMA network may implement a radio technology suchas Global System for Mobile Communications (GSM). An OFDMA network mayimplement a radio technology such as Evolved UTRA (E-UTRA), IEEE 802.11,IEEE 802.16, IEEE 802.20, Flash-OFDM®, etc. UTRA, E-UTRA, and GSM arepart of Universal Mobile Telecommunication System (UMTS). The teachingsherein may be implemented in a 3GPP Long Term Evolution (LTE) system, anUltra-Mobile Broadband (UMB) system, and other types of systems. LTE isa release of UMTS that uses E-UTRA. UTRA, E-UTRA, GSM, UMTS and LTE aredescribed in documents from an organization named “3rd GenerationPartnership Project” (3GPP), while cdma2000 is described in documentsfrom an organization named “3rd Generation Partnership Project 2”(3GPP2). Although certain aspects of the disclosure may be describedusing 3GPP terminology, it is to be understood that the teachings hereinmay be applied to 3GPP (e.g., Re199, Re15, Re16, Re17) technology, aswell as 3GPP2 (e.g., 1xRTT, 1xEV-DO RelO, RevA, RevB) technology andother technologies.

The teachings herein may be incorporated into (e.g., implemented withinor performed by) a variety of apparatuses (e.g., nodes). In someaspects, a node (e.g., a wireless node) implemented in accordance withthe teachings herein may comprise an access point or an access terminal.

For example, an access terminal may comprise, be implemented as, orknown as user equipment, a subscriber station, a subscriber unit, amobile station, a mobile, a mobile node, a remote station, a remoteterminal, a user terminal, a user agent, a user device, or some otherterminology. In some implementations an access terminal may comprise acellular telephone, a cordless telephone, a session initiation protocol(SIP) phone, a wireless local loop (WLL) station, a personal digitalassistant (PDA), a handheld device having wireless connectioncapability, or some other suitable processing device connected to awireless modem. Accordingly, one or more aspects taught herein may beincorporated into a phone (e.g., a cellular phone or smart phone), acomputer (e.g., a laptop), a portable communication device, a portablecomputing device (e.g., a personal data assistant), an entertainmentdevice (e.g., a music device, a video device, or a satellite radio), aglobal positioning system device, or any other suitable device that isconfigured to communicate via a wireless medium.

An access point may comprise, be implemented as, or known as a NodeB, aneNodeB, a radio network controller (RNC), a base station (BS), a radiobase station (RBS), a base station controller (BSC), a base transceiverstation (BTS), a transceiver function (TF), a radio transceiver, a radiorouter, a basic service set (BSS), an extended service set (ESS), amacro cell, a macro node, a Home eNB (HeNB), a femto cell, a femto node,a pico node, or some other similar terminology.

In some aspects a node (e.g., an access point) may comprise an accessnode for a communication system. Such an access node may provide, forexample, connectivity for or to a network (e.g., a wide area networksuch as the Internet or a cellular network) via a wired or wirelesscommunication link to the network. Accordingly, an access node mayenable another node (e.g., an access terminal) to access a network orsome other functionality. In addition, it should be appreciated that oneor both of the nodes may be portable or, in some cases, relativelynon-portable.

Also, it should be appreciated that a wireless node may be capable oftransmitting and/or receiving information in a non-wireless manner(e.g., via a wired connection). Thus, a receiver and a transmitter asdiscussed herein may include appropriate communication interfacecomponents (e.g., electrical or optical interface components) tocommunicate via a non-wireless medium.

A wireless node may communicate via one or more wireless communicationlinks that are based on or otherwise support any suitable wirelesscommunication technology. For example, in some aspects a wireless nodemay associate with a network. In some aspects the network may comprise alocal area network or a wide area network. A wireless device may supportor otherwise use one or more of a variety of wireless communicationtechnologies, protocols, or standards such as those discussed herein(e.g., CDMA, TDMA, OFDM, OFDMA, WiMAX, Wi-Fi, and so on). Similarly, awireless node may support or otherwise use one or more of a variety ofcorresponding modulation or multiplexing schemes. A wireless node maythus include appropriate components (e.g., air interfaces) to establishand communicate via one or more wireless communication links using theabove or other wireless communication technologies. For example, awireless node may comprise a wireless transceiver with associatedtransmitter and receiver components that may include various components(e.g., signal generators and signal processors) that facilitatecommunication over a wireless medium.

The functionality described herein (e.g., with regard to one or more ofthe accompanying figures) may correspond in some aspects to similarlydesignated “means for” functionality in the appended claims. Referringto FIGS. 13-17, apparatuses 1300, 1400, 1500, 1600, and 1700 arerepresented as a series of interrelated functional modules. Here, aradiofrequency signal receiving module 1302 may correspond at least insome aspects to, for example, a receiver as discussed herein. A beacontransmit power determining module 1304 may correspond at least in someaspects to, for example, a transmit power controller as discussedherein. A beacon burst signal transmitting module 1306 may correspond atleast in some aspects to, for example, a transmitter as discussedherein. A radiofrequency signal receiving module 1402 may correspond atleast in some aspects to, for example, a receiver as discussed herein. Atotal received signal power determining module 1404 may correspond atleast in some aspects to, for example, a transmit power controller asdiscussed herein. A beacon transmit power determining module 1406 maycorrespond at least in some aspects to, for example, a transmit powercontroller as discussed herein. An Sintersearch parameter receivingmodule 1408 may correspond at least in some aspects to, for example, areceiver as discussed herein. A Qqualmin parameter receiving module 1410may correspond at least in some aspects to, for example, a receiver asdiscussed herein. A first transmit power defining module 1502 maycorrespond at least in some aspects to, for example, a transmit powercontroller as discussed herein. A second transmit power defining module1504 may correspond at least in some aspects to, for example, a transmitpower controller as discussed herein. A first beacon transmit powerdefining module 1506 may correspond at least in some aspects to, forexample, a transmit power controller as discussed herein. A secondbeacon transmit power defining module 1508 may correspond at least insome aspects to, for example, a transmit power controller as discussedherein. A timing synchronizing module 1510 may correspond at least insome aspects to, for example, a transmitter as discussed herein. A firstminimum signal quality parameter receiving module 1512 may correspond atleast in some aspects to, for example, a receiver as discussed herein. Asecond minimum signal quality parameter receiving module 1514 maycorrespond at least in some aspects to, for example, a receiver asdiscussed herein. A search parameter receiving module 1516 maycorrespond at least in some aspects to, for example, a receiver asdiscussed herein. A minimum required signal quality parameter receivingmodule 1602 may correspond at least in some aspects to, for example, areceiver as discussed herein. A transmit power determining module 1604may correspond at least in some aspects to, for example, a transmitpower controller as discussed herein. A radiofrequency signal receivingmodule 1606 may correspond at least in some aspects to, for example, areceiver as discussed herein. A signal identifying module 1608 maycorrespond at least in some aspects to, for example, a transmit powercontroller as discussed herein. A received energy determining module1610 may correspond at least in some aspects to, for example, a transmitpower controller as discussed herein. A received pilot energydetermining module 1612 may correspond at least in some aspects to, forexample, a transmit power controller as discussed herein. Aradiofrequency signal receiving module 1702 may correspond at least insome aspects to, for example, a receiver as discussed herein. A signalidentifying module 1704 may correspond at least in some aspects to, forexample, a transmit power controller as discussed herein. A receivedenergy determining module 1706 may correspond at least in some aspectsto, for example, a transmit power controller as discussed herein. Atransmit power determining module 1708 may correspond at least in someaspects to, for example, a transmit power controller as discussedherein. A received pilot energy determining module 1710 may correspondat least in some aspects to, for example, a transmit power controller asdiscussed herein. A burst signal transmitting module 1712 may correspondat least in some aspects to, for example, a transmitter as discussedherein.

The functionality of the modules of FIGS. 13-17 may be implemented invarious ways consistent with the teachings herein. In some aspects thefunctionality of these modules may be implemented as one or moreelectrical components. In some aspects the functionality of these blocksmay be implemented as a processing system including one or moreprocessor components. In some aspects the functionality of these modulesmay be implemented using, for example, at least a portion of one or moreintegrated circuits (e.g., an ASIC). As discussed herein, an integratedcircuit may include a processor, software, other related components, orsome combination thereof. The functionality of these modules also may beimplemented in some other manner as taught herein. In some aspects oneor more of any dashed blocks in FIGS. 13-17 are optional.

It should be understood that any reference to an element herein using adesignation such as “first,” “second,” and so forth does not generallylimit the quantity or order of those elements. Rather, thesedesignations may be used herein as a convenient method of distinguishingbetween two or more elements or instances of an element. Thus, areference to first and second elements does not mean that only twoelements may be employed there or that the first element must precedethe second element in some manner. Also, unless stated otherwise a setof elements may comprise one or more elements. In addition, terminologyof the form “at least one of: A, B, or C” used in the description or theclaims means “A or B or C or any combination of these elements.”

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill would further appreciate that any of the variousillustrative logical blocks, modules, processors, means, circuits, andalgorithm steps described in connection with the aspects disclosedherein may be implemented as electronic hardware (e.g., a digitalimplementation, an analog implementation, or a combination of the two,which may be designed using source coding or some other technique),various forms of program or design code incorporating instructions(which may be referred to herein, for convenience, as “software” or a“software module”), or combinations of both. To clearly illustrate thisinterchangeability of hardware and software, various illustrativecomponents, blocks, modules, circuits, and steps have been describedabove generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the aspects disclosed herein may be implementedwithin or performed by an integrated circuit (IC), an access terminal,or an access point. The IC may comprise a general purpose processor, adigital signal processor (DSP), an application specific integratedcircuit (ASIC), a field programmable gate array (FPGA) or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, electrical components, optical components,mechanical components, or any combination thereof designed to performthe functions described herein, and may execute codes or instructionsthat reside within the IC, outside of the IC, or both. A general purposeprocessor may be a microprocessor, but in the alternative, the processormay be any conventional processor, controller, microcontroller, or statemachine. A processor may also be implemented as a combination ofcomputing devices, e.g., a combination of a DSP and a microprocessor, aplurality of microprocessors, one or more microprocessors in conjunctionwith a DSP core, or any other such configuration.

It is understood that any specific order or hierarchy of steps in anydisclosed process is an example of a sample approach. Based upon designpreferences, it is understood that the specific order or hierarchy ofsteps in the processes may be rearranged while remaining within thescope of the present disclosure. The accompanying method claims presentelements of the various steps in a sample order, and are not meant to belimited to the specific order or hierarchy presented.

In one or more exemplary embodiments, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by acomputer. By way of example, and not limitation, such computer-readablemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage or other magnetic storage devices, or anyother medium that can be used to carry or store desired program code inthe form of instructions or data structures and that can be accessed bya computer. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.Disk and disc, as used herein, includes compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk and blu-ray discwhere disks usually reproduce data magnetically, while discs reproducedata optically with lasers. Combinations of the above should also beincluded within the scope of computer-readable media. It should beappreciated that a computer-readable medium may be implemented in anysuitable computer-program product.

The previous description of the disclosed aspects is provided to enableany person skilled in the art to make or use the present disclosure.Various modifications to these aspects will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other aspects without departing from the scope of thedisclosure. Thus, the present disclosure is not intended to be limitedto the aspects shown herein but is to be accorded the widest scopeconsistent with the principles and novel features disclosed herein.

1. A method of communication, comprising: receiving a radiofrequencysignal at an access point, wherein the radio frequency signal includesat least one parameter; and determining beacon transmit power for theaccess point based on the received at least one parameter.
 2. The methodof claim 1, wherein the at least one parameter comprises a value that isdefined to control how an access terminal searches for other cells. 3.The method of claim 2, wherein the at least one parameter comprises anSintersearch parameter.
 4. The method of claim 2, further comprisingtransmitting a beacon burst signal based on the determined beacontransmit power.
 5. The method of claim 4, wherein the determination ofthe beacon transmit power is further based on a defined path losstarget.
 6. The method of claim 5, wherein the determination of thebeacon transmit power comprises providing a transmit power that resultsin the search for the other cells being triggered if the access terminalis closer than the defined path loss target to the access point.
 7. Themethod of claim 1, wherein the at least one parameter specifies aminimum signal quality for an access terminal to sustain a call withanother access point.
 8. The method of claim 7, wherein the at least oneparameter comprises a Qqualmin parameter.
 9. The method of claim 7,wherein the beacon transmit power comprises a lower power level of amultilevel beacon transmit power scheme.
 10. The method of claim 9,wherein the determination of the beacon transmit power is further basedon a defined path loss target.
 11. The method of claim 10, wherein thedefined path loss target corresponds to an outage region within whichtransmission of a beacon by the access point causes call drops for anaccess terminal, and outside of which transmission of a beacon by theaccess point does not cause call drops for the access terminal.
 12. Themethod of claim 1, wherein the access point comprises a femto accesspoint.
 13. An apparatus for communication, comprising: a receiverconfigured to receive a radiofrequency signal at an access point,wherein the radio frequency signal includes at least one parameter; anda transmit power controller configured to determine beacon transmitpower for the access point based on the received at least one parameter.14. The apparatus of claim 13, wherein the at least one parametercomprises a value that is defined to control how an access terminalsearches for other cells.
 15. The apparatus of claim 14, wherein the atleast one parameter comprises an Sintersearch parameter.
 16. Theapparatus of claim 13, wherein the at least one parameter specifies aminimum signal quality for an access terminal to sustain a call withanother access point.
 17. The apparatus of claim 16, wherein the atleast one parameter comprises a Qqualmin parameter.
 18. An apparatus forcommunication, comprising: means for receiving a radiofrequency signalat an access point, wherein the radio frequency signal includes at leastone parameter; and means for determining beacon transmit power for theaccess point based on the received at least one parameter.
 19. Theapparatus of claim 18, wherein the at least one parameter comprises avalue that is defined to control how an access terminal searches forother cells.
 20. The apparatus of claim 19, wherein the at least oneparameter comprises an Sintersearch parameter.
 21. The apparatus ofclaim 18, wherein the at least one parameter specifies a minimum signalquality for an access terminal to sustain a call with another accesspoint.
 22. The apparatus of claim 21, wherein the at least one parametercomprises a Qqualmin parameter.
 23. A computer-program product,comprising: computer-readable medium comprising code for causing acomputer to: receive a radiofrequency signal at an access point, whereinthe radio frequency signal includes at least one parameter; anddetermine beacon transmit power for the access point based on thereceived at least one parameter.
 24. The computer-program product ofclaim 23, wherein the at least one parameter comprises a value that isdefined to control how an access terminal searches for other cells. 25.The computer-program product of claim 24, wherein the at least oneparameter comprises an Sintersearch parameter.
 26. The computer-programproduct of claim 23, wherein the at least one parameter specifies aminimum signal quality for an access terminal to sustain a call withanother access point.
 27. The computer-program product of claim 26,wherein the at least one parameter comprises a Qqualmin parameter.
 28. Amethod of communication, comprising: receiving radiofrequency signals ona radio channel at an access point; determining total received signalpower associated with the radio channel based on the receivedradiofrequency signals; and determining beacon transmit power for theaccess point based on the total received signal power and a definedoutage radius parameter.
 29. The method of claim 28, wherein the definedoutage radius parameter comprises a defined path loss target.
 30. Themethod of claim 29, wherein the defined path loss target corresponds toan outage region within which transmission of a beacon by the accesspoint causes call drops for an access terminal, and outside of whichtransmission of a beacon by the access point does not cause call dropsfor the access terminal.
 31. The method of claim 30, wherein the definedpath loss target is defined based on deployment of the access point. 32.The method of claim 30, wherein the defined path loss target is definedbased on a location of the access point.
 33. The method of claim 28,wherein the beacon transmit power comprises a lower power level of amultilevel beacon transmit power scheme.
 34. The method of claim 28,further comprising: receiving an Sintersearch parameter, wherein thedetermination of the beacon transmit power is further based on theSintersearch parameter; and receiving a Qqualmin parameter, wherein thedetermination of the beacon transmit power is further based on theQqualmin parameter.
 35. The method of claim 28, wherein the reception ofthe radiofrequency signals comprises receiving signals from a pluralityof access points.
 36. The method of claim 28, wherein the access point:transmits a beacon signal on the radio channel based on the determinedbeacon transmit power; and transmits data on another radio channel. 37.The method of claim 28, wherein the access point comprises a femtoaccess point.
 38. An apparatus for communication, comprising: a receiverconfigured to receive radiofrequency signals on a radio channel at anaccess point; and a transmit power controller configured to determinetotal received signal power associated with the radio channel based onthe received radiofrequency signals, and further configured to determinebeacon transmit power for the access point based on the total receivedsignal power and a defined outage radius parameter.
 39. The apparatus ofclaim 38, wherein the defined outage radius parameter comprises adefined path loss target.
 40. The apparatus of claim 39, wherein thedefined path loss target corresponds to an outage region within whichtransmission of a beacon by the access point causes call drops for anaccess terminal, and outside of which transmission of a beacon by theaccess point does not cause call drops for the access terminal.
 41. Theapparatus of claim 40, wherein the defined path loss target is definedbased on deployment of the access point.
 42. The apparatus of claim 38,wherein the receiver is further configured to: receive an Sintersearchparameter, wherein the determination of the beacon transmit power isfurther based on the Sintersearch parameter; and receive a Qqualminparameter, wherein the determination of the beacon transmit power isfurther based on the Qqualmin parameter.
 43. An apparatus forcommunication, comprising: means for receiving radiofrequency signals ona radio channel at an access point; means for determining total receivedsignal power associated with the radio channel based on the receivedradiofrequency signals; and means for determining beacon transmit powerfor the access point based on the total received signal power and adefined outage radius parameter.
 44. The apparatus of claim 43, whereinthe defined outage radius parameter comprises a defined path losstarget.
 45. The apparatus of claim 44, wherein the defined path losstarget corresponds to an outage region within which transmission of abeacon by the access point causes call drops for an access terminal, andoutside of which transmission of a beacon by the access point does notcause call drops for the access terminal.
 46. The apparatus of claim 45,wherein the defined path loss target is defined based on deployment ofthe access point.
 47. The apparatus of claim 43, further comprising:means for receiving an Sintersearch parameter, wherein the determinationof the beacon transmit power is further based on the Sintersearchparameter; and means for receiving a Qqualmin parameter, wherein thedetermination of the beacon transmit power is further based on theQqualmin parameter.
 48. A computer-program product, comprising:computer-readable medium comprising code for causing a computer to:receive radiofrequency signals on a radio channel at an access point;determine total received signal power associated with the radio channelbased on the received radiofrequency signals; and determine beacontransmit power for the access point based on the total received signalpower and a defined outage radius parameter.
 49. The computer-programproduct of claim 48, wherein the defined outage radius parametercomprises a defined path loss target.
 50. The computer-program productof claim 49, wherein the defined path loss target corresponds to anoutage region within which transmission of a beacon by the access pointcauses call drops for an access terminal, and outside of whichtransmission of a beacon by the access point does not cause call dropsfor the access terminal.
 51. The computer-program product of claim 50,wherein the defined path loss target is defined based on deployment ofthe access point.
 52. The computer-program product of claim 48, whereinthe computer-readable medium further comprises code for causing thecomputer to: receive an Sintersearch parameter, wherein thedetermination of the beacon transmit power is further based on theSintersearch parameter; and receive a Qqualmin parameter, wherein thedetermination of the beacon transmit power is further based on theQqualmin parameter.